1. Field of the Invention
This invention relates to an apparatus and a method for detecting the surface profile and the electric properties of a specimen by means of a scanning probe unit (which may be a multi-probe unit) utilizing the physical phenomenon that occurs when a probe is brought close to the specimen. The present invention also relates to an apparatus and a method for observing such a phenomenon. More particularly, the present invention relates to an apparatus and a method for detecting the surface profiles and the electric properties of a specimen by means of a scanning probe unit having a piezoelectric resistance cantilever, which observes the atomic force and the electric current arising as a result of the interaction of the probe and the specimen to detect micro-undulations and/or the electric properties of a micro-region on the surface of the specimen from the changes in the signals of such observation.
2. Related Background Art
The development in recent years of the scanning probe microscope (to be referred to as SPM hereinafter) for directly observing the electronic structure of the surface and its neighborhood of a specimen by utilizing the physical phenomenon that appears when a probe is brought close to the specimen has made it possible to obtain a real spatial image of a physical quantity of the specimen with high. resolution, regardless if it is of a single crystal substance or of an amorphous substance. The principle which provides the high resolution of the SPM with atomic or molecular level has attracted the attention of the industry and efforts have been paid to feasibly apply it to information recording/reproducing apparatus using a recording medium carrying a recording layer. Japanese Patent Application Laid-Open Nos. 63-161552 and 63-161553 disclose such apparatus. Additionally, as a result of the recent technological development in the field manufacturing ICs, the elements contained in such devices have dimensions of sub-microns, and consequently the SPM technology has been used to evaluates processes for manufacturing such devices. Meanwhile, apparatus to be used for such observation and evaluation purposes is mostly designed to observe both the surface profile and the electric properties of a specimen. When, for instance, observing various aspects of an element prepared by lithography, it may be be necessary to examine the electric properties, the profile of the wires, and the dose of the semiconductor element. Then, both an AFM and an STM may have to be used to observe the surface profile and the electric properties of micro-regions of such an element.
However, when the area to be accessed is very small and both a probe for observing the surface profile of the micro-region and a probe for observing the electric properties of the region are used for the same target area, they have to be rigorously aligned relative to that area and also to each other. To avoid this cumbersome operation, there has been proposed a technology of using a single AFM probe that can obtain both information on the profile of a micro-region and electric information of the region. For instance, an AFM probe coated with metal film that can be used for both an AFM (atomic force microscope) using an optical lever and an STM (scanning tunnelling microscope) for observing electric current is known. A number of AFM probes may have to be arranged in parallel (multi-probe arrangement) for practical applications if the throughput of the process has to be improved. As a matter of fact, such arrangements provide research and development objectives in recent years. Studies are being made to employ conventional semiconductor processes for preparing such probes. For example, in view of the fact that a multi-probe detector having a detection system that comprises a plurality of AFMs carrying an optical lever normally requires a very complex optical system and hence is very large, there has been proposed a system for detecting the quantity of deflection of the lever by detecting the change in the resistance of the piezo resistor of a strain gauge arranged on the AFM optical lever.
As discussed above, an apparatus to be used for the evaluation of a semiconductor device is required to comprise a plurality of combinations of an AFM for observing the profile of the device and an STM for observing the electric properties of the device. However, in such known apparatus comprising AFMs, the same optical lever has to be used for the AFM carrying a piezo resistor (to be referred to as piezo resistance AFM) and also for the STM for detecting the electric properties of the specimen. Then, the lever requires a path (wires) and a detection circuit for detecting the piezo resistance and also a path and a detection circuit for detecting the micro-current. The net result is the need of a very complex process for preparing such an apparatus if the probe and the detection circuits are arranged in a single chip.
In view of the above described circumstances, it is therefore an object of the present invention to provide an apparatus and a method for detecting the surface profile and the electric properties of a specimen by means of a detection system comprising a scanning probe and a wiring arrangement having a simplified configuration and detection circuits, which make the system feasible to be used for a multi-probe type system. Another object of the present invention is to provide an apparatus and a method for observing a specimen by utilizing such a detection apparatus and/or such a method.
According to the invention, the above objects are achieved by providing a detection apparatus for detecting the surface of a specimen by means of a cantilever having a probe and a piezo resistance element, said apparatus comprising:
a first circuit for detecting an electric current flowing through said piezo resistance element; and
a second circuit for detecting the electric current flowing through said probe; wherein
the electric current flowing through said piezo resistance element and the electric current flowing through said probe are detected by way of a common current path.
According to the invention, there is also provided an observation apparatus comprising a detection apparatus according to the invention.
In another aspect of the invention, there is provided a detection method for detecting the surface of a specimen by means of a cantilever having a probe and a piezo resistance element, said method comprising the steps of:
detecting an electric current flowing through said piezo resistance element; and
detection an electric current flowing through said probe; wherein
the electric current flowing through said piezo resistance element and the electric current flowing through said probe are detected by way of a common current path.